1 Field of the Invention
This invention relates to an electric soldering iron, and more particularly to an electric soldering iron having a structure capable of preventing electrostatic disturbances of electronic components such as semiconductor elements and electronic appliances due to static electricity charged on the user of the soldering iron or static electricity charged on the soldering iron itself.
2. Description of the Prior Art
It is known well that, in soldering work of electronic components such as semiconductor elements or electronic appliances, the static electricity charged on the user causes electrostatic disturbances such as electrostatic breakdown of electronic components or reduction of reliability.
Conventionally, to prevent such electrostatic disturbances, the user wound a wrist trap with earth wire around his arm to ground it, or the tip of the electric soldering iron was grounded by means of an earth wire, as measures against static electricity.
These measures against static electricity, however, involved the following problems, and their improvements have been demanded.
That is, in the former measure, it is necessary to connect an earth wire to the body of the user, which may give rise to an extreme drop of the job efficiency for the operator who leaves is position often or for the operator working at various places.
In the latter measure, since the main aim of the earth wire is to remove the leak of the current in the heating system of the soldering iron, and it is not necessarily enough to remove the static electricity from the body of the operator.
In this respect, recently, electric soldering irons having a structure as shown in FIG. 3 have been invented (for example, the Japanese Utility Model Publications Nos. 61-22260 and 58-119964).
In this soldering iron, a conductor part b is provided on the surface of a grip a, and the conductor part b can be grounded from the earth wire c by way of the grounding clip d, so that the static electricity charge on the user is discharged in the sequence of the conductor part b, earth wire c, and grounding clip d. The symbol e denotes the tip of soldering iron, f is a heater, g is a power cord, and h is a three-pin plug.
Incidentally, the static electricity charge on the body of the operator is most likely to cause electrostatic disturbances, and recently as a result of development of electronic appliances, the very feeble static electricity generated in the power cord g cannot be ignored, and therefore even the structure of the soldering iron shown in FIG. 3 is not perfect as a means of prevention of static electricity, and a further improvement has been demanded.